New Insights into the Nature of the 5q- Deletion Syndrome Based on Quantitative Measurement of BAALC- Expressing Stem Cell Burdens

A discovery of nonrandom recurrent interstitial aberration at the long arm of chromosome 5 was made by Van den Berghe et al. in 1974. For a long time, this entity was classified as myelodysplastic syndrome (MDS). Meanwhile, its definition as well as classification criteria were repeatedly changed due to both clinical studies and advances in new techniques. In particular an insufficiency of ribosome-forming protein (RPS14) gene was found soon after similar gene RPS19 discovery in patients with severe inherited Diamond-Blackfan anemia (DBA). It cannot be excluded that basic pathogenetic mechanisms, including participation of activated gene TP53, seem to be similar in both entities. This article for the first time presents the quantitative data on the BAALC expression in the majority (25/31) of patients tested with 5q- deletions to be under the cut-off values. It concerns a group of 14/16 patients with isolated 5q- anomaly, and 11 other cases in whom 5q- deletion was combined with additional non-identical chromosomal aberrations. On the contrary, this molecular parameter exceeded the cut-off levels in all (n=10) MDS patients without 5q- abnormality. Hence, these data might effectively support an assumption of a ribosomopathy in cases of isolated 5q- deletion. Since about 8-10 % of these patients are transformed into MDS and/or secondary AML, a possible exclusion of isolated 5q- deletion syndrome from MDS category should be discussed carefully and this assumption is needed an additional support in larger studies.